A new structure model of cross-linked rubber named “Gel- network structure model of cross-linked rubber” is proposed by the author, which is exactly different from a conventional molecular network structure model(Fig.4), as follows. (1) Gel network structure in cross-linked rubber is produced through a gelation process that gel-balls initiated randomly connect each other to make three-dimensional networks of gel-balls(Fig.12~Fig.14) . The gel network structure consists of three different regions, the gel-balls of very highly cross-linked, the molecular bundles of slightly cross-linked which connect the gel-balls each other and the uncross-linked regions(Fig.11). (2) The rigid gel-ball doesn’t deform under extension, but instead the dynamic behavior to generate the deformation of the system is produced by the extension and retraction of the molecular bundles of slightly cross-linked between the gel-balls, which produces the entropic force of the system. The uncross-linked region surrounded by the gel-balls is regarded as the passage where the uncross-linked rubber molecules flow freely under the extension. (3) The gel-ball network structure model is similar to the beads structure where the rigid gel-balls are connected with soft rubber strings (Fig.15) , such structures being observed in several polymer gels(Fig.16~Fig.18).